Hello
I use this site http://www.attracta.com
(In addition to Google Webmaster Tools.)
To analyze my site for obtaining good results in Google.
The results of the analysis i receive the following diagnosis:

Duplicate meta description tags
At -988 pages!

Duplicate title tags
At -950 pages!

A. Does that make sense?
B. If so, how do I remove the duplicate? I canceled my description of the general meta in the general settings and still I get the above result.
So what still appears to me that I have duplicates meta & titles at -988 page?
What's the problem and what the solution?

Attracta seo tool tells which these pages are.
One common reason for this is pagination.
For example you have these links:
[yoursite]/index.php?option=your_com&page=2
[yoursite]/index.php?option=your_com&page=3

If anyone else hits this issue the first thing to look at, is if you have a calendar or event component installed.

I've worked with some components that have links it the calendar boxes where the field is empty, meaning hundreds and even thousands of duplicate titles and descriptions that are blank or default content. Google will find all of these duplicate links if you are not careful.

Such a big number of duplicates is not normal, try to remove your SITE META DESCRIPTION from your Joomla Global configuration page, it tends to be duplicated in most pages that do not have a meta description.